LOS ANGELES (AP) — Scientists say sampling of the Martian atmosphere by the Curiosity rover confirms it’s mostly made of carbon dioxide with hints of other gases.

The measurements appearing in today’s issue of the journal Science are in line with what the twin Viking landers found more than 30 years ago. They’re also similar to what scientists have gleaned from Martian rock fragments that have fallen to Earth.

Mars’ atmosphere is 95 percent carbon dioxide. Earth’s air is a mix of nitrogen and oxygen.

There was one surprise. While Viking found nitrogen to be the second most abundant gas in the Martian air, Curiosity’s measurements revealed a nearly equal abundance of nitrogen and another gas.

Scientists say the slight difference may be due to the different tools used to sample the Martian atmosphere.